Effect of approach velocity on impingement of juvenile Northern pike at water intake screens
approach velocity, impingement, intake, juvenile, irrigation, intake screens, screens, environmental conditions, swim tunnel, water velocity, structures, injuries, mortality, regulations
Journal or Book Title
North American Journal of Fisheries Management
Current guidelines with respect to the use of irrigation intakes limit Canadian operatorsto approach velocities (at the screen) of 3.8 cm/s; however, this value is based on relatively littledata. To address this issue, I examined the ability of juvenile (2.3–7.4-cm fork length) northernpike (Esox lucius) to avoid impingement on irrigation intake screens under ambient environmentalconditions in a swim tunnel (where water velocity was constant and uniform) and in a simulatedintake where water velocity declined with distance from the test screen (as in real structures). Theeffects of impingement duration (in swim tunnel tests) and approach velocity (in both tests) onfeeding and physical condition (abrasions, bruising, and scale loss) were also examined. Juvenilenorthern pike in the swim tunnel became impinged at speeds ranging from 10 to 28 cm/s. Injuriesand mortalities from impingement up to 10 min in duration were nonexistent, although someshort-term feeding disruptions were observed. Northern pike tested in the intake simulationapparatus never became impinged when the approach velocity was 15 cm/s; however, someimpingement (but no feeding disruptions, injuries, or mortalities) was observed at an approachvelocity of 25 cm/s. At higher velocities, impingement, feeding disruptions, injuries, and mortalitiesoccurred. Environmental regulations pertaining to approach velocity at irrigation intake screenscan be set as high as 15 cm/s without adversely affecting juvenile northern pike.